1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device.
2. Description of the Related Art
In MOSFET technology, device miniaturization has proceeded to achieve higher performance. However, there is a limit to the scaling of the gate insulating film in a device of the 0.1 μm generation and later. This results from actualization of an increase of gate leakage current due to tunnel current as the gate insulating film gets thinner. Further, in this generation, depletion of the gate electrode cannot be ignored, and it became difficult to achieve a decreased effective thickness of the gate insulating film. Specifically, as shown in the ITRS Road Map of 2003, it is difficult to implement a transistor with a conventional polycrystalline silicon electrode in a physical film thickness region of less than 1.0 nm.
As methods to avoid these problems, increasing the permittivity of the gate insulating film and using a metal gate electrode are considered. The former is to increase the physical film thickness and to suppress the tunnel current by replacing the gate insulating film with a high dielectric film. The latter is to prevent depletion in the gate electrode by metallization of the gate electrode. Recently, materials development especially on high dielectric gate insulating films has been vigorously pursued, new materials such as ZrO2 and HfO2 has been presented at academic meetings, and decreasing the thickness of an effective oxide film is the object of commercial competitor. However, a sufficient inspection of characteristics including reliability of these materials, like that of the conventional silicon oxide film, has not been done.
Although the investigation of the above-described metal gate electrode is slower than the development of the high dielectric film, the ratio of the depletion in the gate electrode against the thickness of the effective oxide film is about 0.3 nm. Thus, development of the metal gate electrode is necessary in order to obtain prolonged use of silicon-based oxide film until this generation.
Especially, a process of a full-silicide electrode disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2004-152995 is superior in consistency to the conventional CMOS process, and competitive development has proceeded. However, in order to completely substitute the conventional CMOS, formation of silicide electrodes having an appropriate work function for each n-MOS transistor and p-MOS transistor is necessary to be formed.